New water tank gets steel-cable treatment
A DYK Inc. operator looks down Thursday as a “prestressing” tower stops circling a 2-million-gallon water tank being completed just west of Kalispell. The tower moves in a circle to wrap steel cable around the tank to make the concrete less likely to crack. John Stang/Daily Inter Lake
Kalispell's new 2-million-gallon water tank should be filled up by late July.
The concrete tank was wrapped in steel cable Thursday to extend its life - possibly up to 100 years.
Kalispell's rapid growth has outstripped what the city's current 100,000-gallon water tank can handle.
The new 22-foot-tall, 132-foot-diameter tank is being finished on a hill on West Valley Drive just west of Kalispell.
Construction began last August before being suspended for winter.
The $2.5 million tank is part of a $3.8 million project that also includes digging a well and installing the pipe system to take the water to the city.
Robert Peccia & Associates did the engineering work and San Diego-based DYK Inc. supervised the construction.
On Thursday, DYK tackled a step of "prestressing" the tank's concrete wall - wrapping steel cable around it with a tall mobile tower that circled the tank numerous times.
DYK is one of the few companies, if not the only one, to use prestressing - even though it is not patented and was first conceived in the 1940s, said Greg Tseng, an engineer with DYK's business development team.
Prestressing involves wrapping 3/8-inch-thick, seven-strand galvanized steel wire around the entire tank from bottom to top, and covering it with a 1 1/2-inch layer of "shotcrete" - a concrete mix sprayed with a hose.
As water fills the tank, it puts pressure on the concrete to try to push it outward. The steel absorbs that pressure so the concrete does not crack. The steel cable also keeps the concrete in the correct shape as it expands and contracts with temperature changes.
The technique enabled the tank's concrete wall to be 10 inches thick instead of the normal 20 inches.
A major undone task is to bury the completed tank so only 18 inches juts above the ground's surface.
Reporter John Stang may be reached at 758-4429 or by e-mail at jstang@dailyinterlake.com